Method of electrostatic color proofing

Abstract

A method of producing positive multicolor proofs electrostetically including the steps of charging a photoconductor, exposing the charged photoconductor to a negative film, forming a latent electrostatic image on the photoconductor, transfer toning said latent image by virtual contact with a donor member carrying an electrostaticially deposited toner layer. The image remaining on the donor member is transferred to the printing stock paper forming the positive proof. Multiple images are formed from successive film negatives and transferred successively on the printing stock. The deposited form layer is split, between the charged areas on the photoconductor and the image areas on the donor member.

What is claimed is: 
     
       1. The method of electrostatographic image reversal wherein a positive print comprising a receptor sheet having image-free areas and image areas formed by color toner deposits is produced from a negative film having opaque areas corresponding to said image-free areas on said print and transparent areas corresponding to said image areas on said print, said method comprising the essential steps of; A. electrostatically charging a photoconductor to deposit thereon uniformly charges of a first polarity;   B. exposing said photoconductor to light through a negative film thereby to discharge said photoconductor in the areas corresponding to said transparent areas of said negative film while retaining said charges theron in areas corresponding to said opaque areas of said negative film;   C. forming a uniform color toner layer of a second polarity on a donor member by electrophoretic deposition;   D. effecting a virtual contact between said photoconductor and said color toner layer on said donor member to thereby transfer portions of said color toner layer to said photoconductor by attraction to said retained charges thereon while preserving said color toner layer on said donor member in the form of color toner deposits in the remaining portion thereof;   E. transferring said color toner deposits from said donor member onto a receptor sheet; and   F. affixing said color toner deposits to said receptor sheet.   
     
     
       2. The method of electrostatographic image reversal according to claims 1 in which the second polarity is opposite the polarity of the charges deposited on the photoconductor. 
     
     
       3. The method of electrostatographic image reversal according to claims 1, wherein said uniform color toner layer on said donor member is formed by electrophoretic deposition to be of predetermined thickness. 
     
     
       4. The method of electrostatographic image reversal according to claims 1, wherein the optical density of said colored toner deposits on said receptor sheets transferred thereto from said donor member is controlled by the thickness of said uniform color toner layer formed on said donor member. 
     
     
       5. The method of electrostatographic image reversal according to claims 1, wherein said photoconductor is contained on a conductive support and wherein said conductive support and said donor member are electrically connected while said photoconductor is contacted with said color toner layer on said donor member to thereby transfer portion of said color toner layer to said photoconductor. 
     
     
       6. The method of electrostatographic image reversal according to claims 1, wherein said photoconductor is contained on a conductive support and wherein said conductive support and said donor member are held at different voltage potentials in relation to each other while said photoconductor is contacted with said color toner layer on PG,19 said donor member to thereby transfer portion of said color toner layer to said photoconductor. 
     
     
       7. The method of electrostatographic image reversal according to claims 1, wherein said color toner deposits are electrostatically transferred from said donor member to said receptor sheet. 
     
     
       8. The method of electrostatographic image reversal as in claim 1 wherein plural negative separation films of subsequent colors and appropriate color toners are used sequentially to produce a multicolor print comprising said receptor sheet having image-free areas and image areas formed by multiple color toner deposits in register with each other, the steps of transferring said toner layer and said color toner deposits respectively being effected in register and the color toner deposits are affixed to said receptor sheet subsequent to the last to be applied deposit, the steps A-F being repeated with the said negative separation films and the appropriate color toners. 
     
     
       9. The method of electrostatographic image reversal according to claim 8 in which the portions of the first color toner layer transferred to the photoconductor are removed therefrom before the next to be applied color toner layer is applied. 
     
     
       10. The method of electrostatographic image reversal wherein a positive mulitcolor print comprising a receptor sheet having image-free areas and image areas formed by multiple color toner deposits is produced from negative color separation films having opaque areas corresponding to said image-free areas of said print and transparent areas corresponding to said image areas of said print, said method comprising the essential steps of; A. electrostatically charging a photoconductor to deposit thereon uniformly charges of a first polarity;   B. exposing said photoconductor to light through and in register with a negative separation film of a first color to thereby discharge said photoconductor in the areas corresponding to said transparent areas of said negative separation film of a first color while retaining said charges thereon in areas corresponding to the opaque areas of said negative separation film of the first color;   C. forming a uniform first color toner layer of second polarity on a donor member by electrophoretic deposition;   D. effecting a virtual contact between said photoconductor in register with said donor member with said first color toner layer on said donor member to thereby transfer portion of said first color toner layer to said photoconductor by attraction to said retained charges thereon while preserving said first color toner layer on said donor member in the form of first color toner deposits in the remaining portion thereof;   E. transferring in register said first color toner deposits from said donor member onto a receptor sheet;   F. removing from said photoconductor said portion of said first color toner layer transferred thereto;   G. repeating above steps A to F with negative separation films of subsequent colors and appropriate subsequent color toners to produce a multicolor print comprising said receptor sheet having image-free areas and image areas formed by multiple color toner deposits in register with each other; and   H. affixing said color toner deposits to said receptor sheet.